1. Field of Invention
This invention relates to the design and construction of structures, specifically to structures with prefabricated deck units.
2. Prior Art
Full-depth precast concrete deck has gained popularity as an accelerated construction method. Use of full-depth precast concrete deck allows for the deck concrete and reinforcement to be placed in a controlled environment, improving the quality of the deck. Since the units are prefabricated, they can be delivered to a site and erected quickly.
Structures using full-depth precast concrete deck typically consist of a plurality of longitudinally spaced concrete deck units supported by longitudinal load-carrying members. This member or members is usually a single girder or multiple girders.
This member or members can be comprised of various materials including steel, concrete, wood or fiber-reinforced plastic.
To improve deck durability, it is important to have a pre-compression force across deck joints to minimize the propensity of the deck to crack under loading. Currently, such pre-compression force is supplied via standard post-tensioning systems, which utilize post-tensioning tendons or bars within ducts. US Federal Highway Administration technical report (#FHWA-IF-09-010) provides a comprehensive summary of current engineering practice using precast deck units, showing that all current precast deck systems with longitudinal compression utilize post-tensioning systems in the deck. Other patent references, such as U.S. Pat. Nos. 7,475,446, 7,461,427, and 5,457,839, illustrate various methods of using post-tensioning system to provide deck compression. However, using standard post-tensioning details carries with it the disadvantage of requiring additional cost and time to construct. This invention provides a more economical solution. The pre-compression force across deck joint is produced not by post-tensioning tendons but by tensioning the supporting girders themselves.